The present invention concerns a flow regulator for gaseous substances, in particular for air in air-conditioning and ventilation installations, for maintaining the volumetric flow of a gaseous substance at desired magnitude with sufficient accuracy, at a differential pressure across the flow regulator varying within given limits, said flow regulator comprising an envelope and a regulating member disposed in a flow passage confined by the envelope.
In low-pressure regulators known in the art, in which the set-point value of volumetric flow can be regulated in a comparatively wide range, the lowest pressure at which the means starts to operate increases with increasing volumetric flow. Even at small volumetric flow rates, the lowest pressure is generally relatively high. The top pressure also increases in accordance with the set-point value of the volumetric flow.
Owing to the lowest pressure which is high and/or which depends on the set-point value of the volumetric flow, regulators of prior art, in order to operate properly, require extra blower energy and potentially a larger blower; they have a great tendency to cause noise problems due to pressure increase, or a need for damping; they impede the designing; they cause difficulties in the implementation phase of the installation.
As a rule, in flow regulators accurate and stepless setting of the volumetric flow rate at the site of installation, particularly if the regulator has already been installed, is extremely cumbersome, and in practice often impossible, nor can the set-point value of the volumetric flow rate be read directly. In regulators of prior art, the throttling pressure with which the regulator throttles the flow cannot be read either. It is true that in certain regulator designs of prior art dwelling within the operating range can be observed from the outside, but their volumetric flow rate cannot be regulated.
A prerequisite of serial manufacturing, storing, distributing and use of the regulator is that the regulators can with ease and accuracy be regulated at the site of installation even after installation. It is important in view of the balancing and inspection of an air conditioning installation that it is possible to observe from outside the regulator which is the set-point value of the volumetric flow rate, whether the regulator is in the operating range, and how strongly the regulator throttles. In addition, the basic construction and manufacturing technique shall be such that the required calibrating measures are as simple and minimal as possible and independent of the setting of the volumetric flow.
In regulators of prior art, the movement of the regulating member cannot be steplessly limited. Therefore, regulators of prior art cannot be used at all for mere balancing without incurring the risk of binding of the means. Secondly, the regulators of prior art cannot be used for restricted and controlled correction. Thirdly, regulators of prior art cannot be used in the best possible way in air-conditioning installations where the air quantities are varied, such as e.g. different air quantities in daytime and night running.
In regulators of prior art, for counterforce of the regulator member is employed either a mass or a spring, or a spring and bellows in combination. Each of these designs has its advantages and disadvantages. Disadvantages when using springs are, for instance, relaxation of the spring, inaccuracies in manufacturing, susceptibility to damage, etc. Disadvantages of a mass used for counterforce have been that the regulator can only be installed in a horizontal duct, that the axis should always be horizontal with reference to the direction of flow, and that the mass must always be on the same side of the duct. Advantages of a mass used for counterforce are, for instance, reliability in use, good manufacturing accuracy and constancy. Disadvantages of spring plus bellows are that the design is more prone to disturbances and more expensive than a mere spring, and has a shorter life span.
In regulators of prior art, for damping out the oscillations of the regulating member, or the so-called hunting, a particular damping means is required. In certain designs of prior art, dashpot type damping is used. In another regulator of prior art, damping of bellows type is used. Disadvantages of the damping designs described above include the fact that the damping designs may bind in the course of time, or they may be blocked or damaged, that the designs require maintenance, and that they may impair the accuracy.